It is of course elementary that all aerobic microbial cells produce energy for the cell through respiration. As cellular respiration occurs, pyridine nucleotides are reduced in the living cells. That reduction can be detected by exciting the microbial cells with electromagnetic radiation in the UV range, and forms a basis for detection of cellular respiration.
In U.S. Pat. No. 4,162,405, which issued on Jul. 24, 1979, there is described a method and apparatus for measuring heterogeneity of oxygen delivery in human and animal tissue. The foregoing patent indicates that it is possible to detect and distinguish reduced nucleotides such as nicotinamide adenine nucleotides or NADH occurring in, for example, brain tissue and other living tissues by means of fluorescence.
With recent announcements of bacterial contamination in meats and poultry, there has been a need to provide a method and apparatus which can be used to detect such microbial contamination in meat and poultry which can be operated inexpensively and rapidly in, for example, meat and poultry production facilities. In U.S. Pat. No. 4,631,413, there is described a technique for examining the surface of meats, fish and the like for bone, fat and cartilage. Cartilage and bone fluoresce at about 390 nm when excited with electromagnetic energy or lightwaves having a wavelength of about 340 nm. The bone, cartilage and connective tissue from some animals, and notably pigs and chicken, exhibit weak fluorescence at about 455 nm; cow fat exhibits weak fluorescence at about 475 nm. The foregoing patent shows that cow meat has essentially no fluorescence in the vicinity of about 440 nm.
Thus, the foregoing patent does not disclose or suggest any technique by which the presence of living microbes exhibits fluorescence around 440 nm with excitation around 366 nm and can be distinguished from meat and poultry tissue which is no longer living.
It is accordingly an object of the invention to provide a method and apparatus which can be used in the detection of microbial contamination in non-living surfaces such as meat and poultry.
It is a more specific object of the invention to provide a method and apparatus for use in the detection of microbial contamination in meat and poultry in which microbial contamination can be determined inexpensively and rapidly in, for example, meat and poultry production facilities.
It is yet another object of the invention to provide a method and apparatus for use in the detection of microbial contamination in meat and poultry in which the fluorescence of reduced nucleotides are excited by electromagnetic radiation to distinguish the metabolic reactions of microbes from the tissue of meat and poultry to allow microbial contamination in meat and poultry to be determined without contact with the meat or poultry.